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Whirling Frequencies and Amplitudes due to Deviations of Generator Shape
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
2008 (English)In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 43, no 9, 933-940 p.Article in journal (Refereed) Published
Abstract [en]

Earlier measurements in large synchronous generators indicate the existence of backward whirling motion, and also relatively large deviations of shape in both the rotor and the stator. These non-symmetric geometries produce an attraction force between the rotor and the stator, called unbalanced magnetic pull (UMP). The target of this paper is to analyse the whirling frequencies and amplitude of the response for large synchronous generators with a high number of poles. due to deviations of shape in the rotor and stator. A mathematical model is developed to describe the shapes of the rotor and stator. and the corresponding LIMP is obtained by using the law of energy conservation. The LIMP is analysed due to different deviations of shape. The result gives the average angular frequency and the magnitude of the UMP for certain deviations of shape. From this result, the whirling frequency and the amplitude of the corresponding response can be approximated. Simulations of the response of a Jeffcott rotor model show good agreement with the theoretical results of the LIMP for some generator geometries. The conclusion is that different whirling frequencies, both backward and forward whirling. can occur in these machines due to deviations in shape of the generator. Therefore, the shape of the generator can excite resonance vibrations on several other frequencies than the rotation frequency. During maintenance of hydropower generators the shapes of the rotor and stator are frequently measured. The results from this paper can be used to evaluate such measurements and to explain the existence of complicated whirling motion.

Place, publisher, year, edition, pages
2008. Vol. 43, no 9, 933-940 p.
National Category
Engineering and Technology
URN: urn:nbn:se:umu:diva-40228DOI: 10.1016/j.ijnonlinmec.2008.07.002ISI: 000261304900016OAI: diva2:398459
Available from: 2011-02-17 Created: 2011-02-17 Last updated: 2014-09-29Bibliographically approved

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Lundström, Niklas
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